New Research: The Glute Max is Really Good at Stabilizing the SI Joint

Low back pain is a bitch! Previous literature suggests that up to 30% of incidences of low back pain could in fact stem from the sacroiliac (SI) joint. I wrote about the SI joint a year and a half ago in a blogpost titled, The Sacroiliac Joint Takes a Beating. If you haven’t read this yet, I recommend you do!

Nevertheless, a recent paper has emerged that sheds more light on the critical role that the gluteus maximus plays in stabilizing the SI joint. The article was published in the Clinical Journal of Biomechanics and is titled, “Anatomy and biomechanics of gluteus maximus and the thoracolumbar fascia at the sacroiliac joint.” Click HERE for the Pubmed link, but I’ll paste the abstract below:

Abstract

Biomechanical models predict that recruitment of gluteus maximus (GMax) will exert a compressive force across the sacroiliac joint (SIJ), yet this muscle requires morphologic assessment. The aims of this study were to document GMax’s proximal attachments and assess their capacity to generate forces including compressive force at the SIJ. In 11 embalmed cadaver limbs, attachments of GMax crossing the SIJ were dissected and their fascicle orientation, length and attachment volume documented. The physiological cross-sectional area (PCSA) of each attachment was calculated along with its estimated maximum force at the SIJ and lumbar spine. GMax fascicles originated from the gluteus medius fascia, ilium, thoracolumbar fascia, erector spinae aponeurosis, sacrum, coccyx, dorsal sacroiliac and sacrotuberous ligaments in all specimens. Their mean fascicle orientation ranged from 32 to 45° below horizontal and mean length from 11 to 18 cm. The mean total PCSA of GMax was 26 cm2 (range 16-36), of which 70% crossed the SIJ. The average maximum force predicted to be generated by GMax’s total attachments crossing each SIJ was 891 N (range 572-1,215), of which 70% (702 N: range 450-1,009) could act perpendicular to the plane of the SIJ. The capacity of GMax to generate an extensor moment at lower lumbar segments was estimated at 4 Nm (range 2-9.5). GMax may generate compressive forces at the SIJ through its bony and fibrous attachments. These may assist effective load transfer between lower limbs and trunk.

WTF Does This Mean?

When muscles contract, they create compressive force, which also creates joint force. This joint force increases stability, which is especially important in the SI joint. If we convert Newtons to pounds (HERE is an online calculator that’ll do it for you), we see that 702 N equates to 158 lbs of force. Actually, the glute max produced 200 lbs of force, but you have to take the angle of the fibers relative to the SI joint into consideration and use geometry to calculate the effective force acting on the SI joint, but I digress. This 158 lbs of force clamps down on the SI joint and keeps it in place during movement. It also acts to increase the transfer of force between the upper and lower limbs, so its practical applications extend to performance and not just injury and pain prevention.

80-Year Old Glutes Don’t Cut it!

However, the study examined 6 elderly cadavers (average age of 80-years old). The average gluteus maximus volume was 389 mL. You may recall an article I wrote 6 months ago on Glute Genetics where one subject possessed a set of glutei maximi with a volume of 958 mL. That’s nearly 2.5 times the volume of the elderly cadavers!

In THIS Russian article (I possess an English version), physically-active 21-year old subjects possessed an average of 907 mL of gluteus maximus volume. What’s very cool is that following 8 weeks of leg press exercise, this volume increased to 1,064 mL, which is an increase of around 17%! Leg presses don’t get you near as much glute activation as hip thrusts, so I’d expect hip thrusts to lead to much greater increases in glute volume. I’m fairly certain that some of my clients have increased their glute volume by over 100% in six months of training. I’m sure that there are various bodybuilders, powerlifters, Olympic weightlifters, strongmen, and NFL lineman with gluteus maximus volumes of 1,500-2,000 mL.

If elderly glutes can produce 200 lbs of muscle force and they’re around a fourth the size of a powerlifter’s, not to mention they don’t activate as well, one could surmise that athletes with incredibly muscular and powerful glutes could produce around 500-600 lbs of force, most of which transfers directly from the gluteus maximus to the stabilization of the SI joint. This stabilization helps prevent injury and pain, in addition to improving force transfer between the upper and lower halves of the body and increasing power production.

Conclusion

If you want to minimize the risk of low back pain and injury, in addition to maximizing performance, make sure you train the glutes hard so they can effectively stabilize the SI joint and prevent aberrant motion from occurring during forceful and explosive movements.

26 Comments

Bret, my lower back pain has definitely decreased since I started focusing on my glutes. In fact, sometimes when I’m in a little pain I will do bridges and hip thrusts and the pain will actually go away. Weird. It’s like I just need the reminder to be activating/using my glutes more.

On a side note, sometimes I wonder if my hip thrust setup isn’t maximal. What is the height measurement of the pad on your new hip thruster? Have you determined that height to be universally ideal, or is there variance depending on body type? Thanks!

Hi Kim! Thanks for the comment. I have 5’0″ clients and 6’6″ clients and all do well with a 16″ height, and it took me many years to determine what I felt was the optimal height (16″) which is why I chose that for my hip thruster. Though body types differ dramatically, the vast majority of people do well at that height.

Great article. There needs to be more research regarding functional strength in the elderly population and how activating and developing the glutes lead to huge improvements in functional movements (walking up stairs and getting out of a chair). Maybe with greater research we can fix that pitiful 389 mL of the gmax. 🙂

Do you have advice for getting the glutes stronger without much hypertrophy?
My glutes starkly overpower my hams and pretty much everything else. I suspect this to be genetic as my thin as rails little brother has fairly noticeable glutes despite lacking overall muscle mass, possibly due to high insertion points.
I however definitely would want to get mine stronger.
Also, do you consider hip thrusts and glute bridges on a same continuum of exercises or as fairly separate exercises?
Thanks!
Thanks!

Leroy, I’d say just stick to low volume and really heavy weight. For example, have one day per week where you do 3 x 5 hip thrusts and that’s it. Yes, hip thrusts and gg glute bridges are on the same continuum.

Great article as always Bret!
Thank you for this interesting information. Bret I think pretty in myofascial release to mention that you could self-release myofascial techniques are the most interesting.

I work in a clinical setting, so for me, the application of most exercises extends to improving ADL and ability to perform functional tasks, not getting sexified.

What would you recommend for improving glute strength in an older population who

a) don’t go to, or have any interest in going to a gym
b) don’t own, and don’t want to purchase any equipment for home
c) don’t have great mobility (find it difficult to get up and down from the floor unassisted)
d) don’t want to spend a lot of time exercising
e) can be performed daily (usually easier to form a habit this way)

Nick, I’d recommend the following: a squatting movement, a hip-hinging movement, a bridging/thrusting movement, and a lateral band movement (I know you said no equipment but bands are cheap). For some this would mean a bilateral bodyweight squat, a bodyweight single leg RDL, a bodyweight glute bridge, and a band seated hip abduction, while for others it could mean a pistol squat, a single leg back extension (if they had a partner to hold down their leg), a single leg hip thrust, and monster walks. Cheers, BC

I taught exercise classes at a senior center and had great success with having the members sit down and rise out of a standard chair, a highly regressed form of box squats. If that was too easy, stability ball squats worked well. We also used elastic bands and did standing hip extension, adduction and abduction.

Hi Bret. I found this article so important to what I do in my day job, and the information jibes with my experience (stronger glutes means less low back pain). I work as a loader/unloader and lift heavy things repeatedly, usually off the floor. So hip hinging is extremely functional for me. I was going to start an abbreviated program (power to the people) but wanted to include lots of hip thrusting. I was thinking three days a week, one day trying for a heavy 10RM on hip thrust or glute bridge (undecided), one day maybe 80% of previous day for 5×20 (ht or gb) and another day where I try for maybe heavier triples followed by a set to failure before the weekend. Sorry the long post and any comments are greatly appreciated. Viva hip thrust!

Hi Bret, I have just recently been turned on to your website and absolutely love it! I always realized the importance of glute training and now have more ammunition than ever thanks to your research and website. 2 questions for you, one is what do you think of single leg presses for glute activation and secondly what do you recommend for loaded bridges to reduce the discomfort on the pelvic area? I am a rather unique case as I have had both of my hips replaced due to a fall from a ladder and 2 bouts of Lymes disease, but weight training has saved my body. I did a lot of single leg presses leading up to my surgery to keep my glutes activated because I lacked stability to do the other exercises but now I have been trying to incorporate some of the others and I am getting great results.

As a lady who has returned to training after a few years..and also in her 50s I have lost weight and want my glute’s back to their strength and fullness..how do I go about my exercise routine now and what would you suggest..I am pain free and have good flex in my joints as I run and lunge monster walk…. I want to get max results within 3 months as getting married and want to look good in my clothes..

Thanks for the advice have ordered Book you suggested..it has rave reviews on amazon…so looking forward to it..weight has incurred a saggy ass..have not had one before always good glutes..so looking forward to this read and implementation of the exercises will keep you informed as to progress and send updates as to my progression.. want results quicker than 6 months so willing to put the extra work in ..

Thanks again for your reply and all the great work you and Kellie do here..

Hey Bret, excellent articles, in my notebook you have an A+, based upon some of your articles my glutei-thights muscle groups are adapting quite well to new training stressing level performing squats below parallel lessening delayed on muscle soreness. I just want to thank you for all you do for us by researching how to develop
the gluteus maximus, et.al Keep the great work….Adrian

This is really interesting, I’ve had some si pain over the last year and have found suitcase walks and wheel rollouts really help, when I do the wheel I squeeze my ass hard and go into ppt, these two exercises must address alot of the issues you speak of.

I appreciate you may be too busy to respond but I’d be extremely grateful if you could because I can’t think of a more qualified person to answer this question.

I injured my back 3 months ago and saw an x-ray of my spine last week. The L5/S1 disk has worn out and the facet joint is touching the sacrum. The doctor said this is due to wear and tear and for my age (30) this should not be the case. I’m terrified that my training has caused this (and focus on glutes) though he said he’d expect to see this type of wear and tear in somebody who has been building for 10 years. In my case I’ve been gymming for 5 but training hard for the past 2 years. It is possible that my posture caused this due to the arch in my back. I’m waiting for a final diagnosis.

He told me to continue exercising but not to go heavier and I can’t squat/deadlift any longer because the load compresses the spine. How would you recommend maintaining the glutes without putting pressure on the L5/S1? Am I still safe to do hip thrusts?

To say I’m devastated is an understatement. I had just signed up to a PT to begin power lifting and the prospect of not being able to do this is very upsetting. I just hope I can continue to gain or at the least maintain. What are your thoughts?